Pressurized fluid systems generally employ metal tubes connected at the ends to fittings. A joint, that should be free of leaks, must be formed at each fitting. Conventionally, this is accomplished by first permanently attaching a ferrule to the tube, usually by hydraulic swaging or by roller swaging. Hydraulic swaging is preferred and is described in U.S. Pats. Nos. 4,407,150; 4,414,739; 4,450,612 and 4,359,889. The ferrule is configured to mate with the fitting. Usually, a retainer nut is used to pull the ferrule and the fitting together axially.
The axial retaining forces, which must overcome the force of the pressurized fluid, are conventionally relied upon to provide the sealing forces by tightly pressing together two abutting surfaces. Seals thus formed are known as "face seals". They may be metal-to-metal seals or they may includes O-rings. However, face seals are prone to leakage because of their dependency on eliminating virtually all axial movement between the ferrule and the fitting.
An objective of the present invention is to provide a method for forming an improved seal for use in pressurized fluid systems that is not dependent upon the elimination of axial movement. A further objective is to provide a method for forming such a seal in which the force of the pressurized fluid tends to close rather than open the seal. A still further objective is to provide a method for forming such a seal that is relatively simple, easily assembled and easily checked for integrity.